In an era of increasing security concerns, biometric-related innovations are becoming increasingly valuable tools for authenticating the identity of individuals. One biometric in particular, the fingerprint, has long been known to be unique to each individual, however others, such as the retinal scan, are gaining increasing use. Traditionally, a “hard copy” of an individual fingerprint was obtained and stored as ink on paper. Many modern methods now exist, however, for obtaining, storing and transmitting fingerprint images electronically.
The obtaining, storing and transmitting of fingerprint images is typically performed as part of an effort to match a sample fingerprint to a master fingerprint. There are currently two generic forms of algorithms for fingerprint matching. The first form of algorithm uses minutiae-based analysis while the second form of algorithm uses pattern-based analysis.
Several patents (such as U.S. Pat. No. 5,239,590 to Yamamoto, U.S. Pat. No. 6,301,376 to Draganoff and U.S. Pat. Nos. 5,363,453 and 6,212,290 to Gagne et al.) disclose pattern-based fingerprint matching algorithms.
Yamamoto describes a fingerprint verification method wherein a sample fingerprint image is separated into a plurality of blocks. Each block is then subdivided into a plurality of areas. For each area, a direction code is determined. The direction codes of areas in a master fingerprint are compared to direction codes of corresponding areas in a sample fingerprint to determine a “dispersion” for each area. Yamamoto describes a data record format in conjunction with the fingerprint verification method. The data record includes an index for each of the blocks, where the index is calculated based on a minimum dispersion area in each block.
Draganoff describes a fingerprint verification method wherein a statistical similarity between an enrolled (master) fingerprint and the (sample) fingerprint to be verified is sought. Initially, a match is sought for a first yardstick in an amount of data representing the fingerprint image to be verified. Yardstick data is moved throughout the image, preferably in a predetermined order, and comparisons are made to find a sufficient match. Once the first yardstick has been matched, the location of the match is known and, because the location of the other yardsticks to be tested is known relative to the position of the first yardstick, the method and apparatus checks other yardsticks in only a limited number of locations.
Gagne et al. describes a non-minutiae-based fingerprint verification method and system wherein a digitised numerical identifier is used to uniquely represent a fingerprint. The digitised numerical identifier is derived from a ridge count taken at various parts of the fingerprint. The digitised numerical identifier described by Gagne et al. may be reduced to 24 bytes to fit among the information contained on a magnetic stripe of a card such as a credit card.
U.S. Pat. Nos. 5,841,888, 5,845,005 and 6,021,211 to Setlak et al. provide a method (and related apparatus) for indexing fingerprints to improve the performance of fingerprint cold-search operations. In particular, ridge flow direction vectors are used to determine a curliness index of a sample fingerprint. The curliness index of the sample fingerprint may then be used to reduce the field of a search for a matching fingerprint.
There remains a need for an efficient data format for storing and transmitting images such as fingerprints.